The present invention relates to a liquid crystal display cell comprising substrates of a flexible film and a method for manufacturing the cell, and, more particularly, to a liquid crystal display cell with a uniform thickness using an intermediate cell in which air bubbles and a sealing material are prevented from entering into the intermediate cell interior through an injection hole of the cell and a method for the manufacture thereof.
The application of liquid crystal display cells to pocket size devices has been steadly expanding and, as a consequence, the need for producing liquid crystal display cells having a reduced weight and thickness has been recognized. At present, liquid crystal display cells primarily use glass substrates, and since these glass substrates lose mechanical strength as the glass decreases in thickness, the manufacture of glass substrate display cells is difficult and the quality of the resultant display cells suffers. As the glass becomes thinner, it is more likely to break. Additionally, from an economic point of view, the price of the glass substrae increases as the wall thickness decreases. To eliminae these problems, a an organic polymer film capable of replacing glass can be used for the substrate. When the organic polymer film is used as the material for the substrates, the need to produce display cells of reduced weight and thickness is satisfied by display cells that will sustain external impacts, such as those caused by a fall, without breaking. Because the organic polymer film is flexible, it naturally follows that the display cells using substrates of this film are flexible. This type of film permits manufacture of display cells for curved surfaces or display cells having freely alterable surface properties which, at the same time, do not break when deformed. The substrates for the display cells must have a certain degree of transparency, thermal resistance, mechanical strength, and stiffness.
However the organic polymer film is used as the material for the substrates, it is difficult to fix the distance between the substrates or the distance separating the electrodes because the film is flexible. When the fabricated liquid crystal cell as described above is left standing for a long period of time or is placed under conditions of widely varying temperature changes, such as encountered in a temperature-humidity cycling test, the liquid crystal cell forms zones in which the two flexible film substrates come into mutual contact and thus short circuits are caused between the electrodes. On the other hand, even though the short circuits could be prevented by, for example, inserting spherical spacers about 10 .mu.m in diameter between the electrodes, the variation in the distance separating the electrodes after the cycling tests, etc. is in the range of about 10 .mu.m to about 100 .mu.m within the same cell. As a consequence, the response time of the display cell varies greatly from one position to another across the surface of display cell and the quality of the display may be seriously reduced.
When the liquid crystal cell is manufactured, the excess liquid crystals may be removed from the cell after the injection of liquid crystals into the cell through an injection hole, by sequentially pressing both surfaces of the cell with rollers of a suitable elastic material in a direction from one side toward the other side, so that cell with a uniform thickness can be manufactured. However, when the injection hole is sealed, the back pressure generated by the following film substrates will cause air bubbles to enter the display cell interior through the injection hole of the cell or excess injection hole sealing material to enter the display cell interior. Therefore, the quality of the display cell may be seriously reduced.